In 25 years of employment, I've come across two bullies. One was not in aviation, but he made it quite clear he didn't respect women. He would go out of his way to belittle female colleagues. I'm not sure he even realised the effect he had: people from other departments would phone ahead to see if he was in the office and make a decision as to whether to visit or not based on his presence. I think that in his case, he felt threatened by the fact that the women doing the same job as him were, in some cases, much better than him.
The other was in aviation. I don't think he did it to compensate for feelings of inadequacy. He did it because he enjoyed making people squirm, he liked needling and prodding and pushing people just to see when and how they would break, just for the sheer pleasure of it. I left that company as soon as I could and was grateful that I had the opportunity to do so. His behaviour was making the flying unsafe, and that is inexcusable in my opinion.